Montana's primary keep-right rule is found in Montana Code Annotated §61-8-321.
On roadways with two or more lanes available for traffic moving in the same direction, a vehicle generally must be driven in the right-hand lane.
A driver may use another lane when overtaking and passing another vehicle, traveling faster than the existing traffic flow, moving left to allow traffic to merge, preparing for a lawful left turn, or taking a left-side exit from a controlled-access highway.
The law also allows another lane when an obstruction, hazardous condition or other roadway circumstance makes right-lane travel impractical or unsafe.
Within the official boundaries of a city or town, the general right-lane requirement does not apply in the same way, subject to other lane-use provisions.
Montana therefore goes beyond a simple slower-traffic rule by generally requiring right-lane travel on qualifying multilane roads unless one of the listed exceptions applies.
Exceptions
- Overtaking and passing another vehicle traveling in the same direction.
- Traveling faster than the existing flow of traffic.
- Moving left to allow traffic to merge onto the roadway.
- Preparing for a lawful left turn.
- Taking a left-side exit from a controlled-access highway.
- Avoiding an obstruction or hazardous roadway condition.
- Traveling within the official boundaries of a city or town where the statutory exception applies.
- Following an official traffic-control device or other lawful lane-use requirement.
Penalties
A violation of Montana's keep-right rule may result in a traffic citation.
Montana's published bond schedule has listed failure to drive to the right or slow traffic under §61-8-321 as a misdemeanor offense with a standard bond amount of $85.
Drivers should verify the current amount shown on the citation or with the court handling the case because schedules and assessments may change.
Official Source
Montana Code Annotated §61-8-321 - Drive on Right Side of Roadway; Exceptions
Last verified: October 11, 2026